Piston ring and method of making same



June 4, 1940. A. T. COLWELL 292029899 PISTON RING AND METHOD OF MAKING SAME Filed March 18, 1938 2 Sheets-Sheet l JECL L31 Q E in].

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June 4, 1940. A. T. COLWELL PISTON RING AND METHOD OF MAKING SAME 2 Sheets-Sheet 2 Filed March 18, 1938 flea/ms- Z' Co: 544

Patented june 4, 1940 UNITED STATES- PISTON RING AND METHOD OF MAKING SAME Archie T. Coltvell, Clevelan Ohio, assiznor to Thompson Products Incorporated, Cleveland, Ohio, a. corporation of Ohio Application March s, 1938, Serial No. 196,631

6 Claims.

This invention relates to a packing ring for pistons, and especially pistons 01 internal combustion engines. More particularly this invention relates to a piston ring having a non-ferrous alloy bearing face for engaging the wall of the cylinder in which the piston is mounted.

It has heretofore beenproposed to coat piston rings with metals to provide cylinder engaging surfaces thereon. These surfaces have generally been formed either by electroplating or by dipping operations. The coatings are usually of relatively soft metals and are of negligible thickness as compared with the thickness of the piston ring holly. Such thin coatings wear away rapidly, anti furthermore cannot present suficient volume for the absorption or appreciable amounts of oil or other lubricant to render the surfaces selfluhricating.

Accorrlhig to this invention, a piston ring is pro-- with an oil-absorbent alloy layer of appreciaole thickness, which is integrally and mrmanently united to the piston ring foundation metal by a welding or brazing operation.

According to the process of this invention, a sheet of steel to form the body portion or a piston ring is integrally welrlecl or brazed to a sheet of an oil-absorbent alloy of non-ferrous The resulting laminated sheet is then out into 9 strips, which are bent into the usual split piston ring shape. If desired, the strips can be wider than is desired for the Width of a piston ring, and thwe wide strips then upset edgeWis-e to reduce the same to piston ring width, while at n the same time, however, increasing the thickness of the strips and also increasing the extent of the area of weld between the welded laminations. The upsetting operation causes the steel portion of the strip to bow into the alloy portion of the strip, thereby presenting a welol area with a curved contour.

In one embodiment of the invention the welding operation is efiectezi in a flash-percussion Welding step wherein an electrostatic discharge is passed through the sheets surfaces thereof a minute, almost monomolecular, depth. The molten surfaces, when brought into percussive engagement, will immecliatelv unite to form a good, permanent weld.

If clesirecl', a hon-ferrous alloy can merely be melted onto a steel sheet in a reducing or nonoxidizing atmosphere so that the alloy will be erased to the sheet anti will form a layer thereon of any desired thickness.

it is, then, an object of this invention to pro= melting the contiguous in Figure 6.

vide a ferrous metal piston ring having an oilabsorbent' alloy layer of appreciable thickness thereon and integrally united therewith.

A further object of this invention is to provide a piston ring composed of steel as the foundation metal and a relatively thick, oil-absorbent alloy layer welded to the outer periphery of the steel to form "a. self-oiling cylinder-engaging bearing face for the ring.

Another object of this invention is to provide a piston ring composed of a ferrous metal body material and a non-ferrous, oil-absorbent alloy integrally welded thereto and rorming the outer periphery thereof.

A further objectof this invention is to provide a steel piston ring having an Oilite strip Welderl to the outer periphery thereof to form a cylinderengaging hearing face for the ring.

Another object of this invention is to provide a process or making piston rings from laminated sheets of metal.

A further object of this invention is to provide a process of making piston rings including the step of laminating sheets of metal or clifierent characteristics by welding operations.

Other and further objects or this invention will become apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings which disclose preferred embodiments of the invention.

On the drawings:

Figure l is a iragmentary isometric view of a sheet of steel to form theborly of a piston ring according to this invention.

figure 2 is a fragmentary isometric view of a sheet of non-ferrous oil-absorbent alloy metal for forming the cylinder-engaging element of piston rings according to this invention.

Figure 3 is a side elevations! View iilustratihg the mounting of the sheets shown in Figures 1. and 2 in a flash-percussion Welding apparatus to insure a good weld therehetvveen.

Figure 4 is a View similar to figure 3 but tllus trating the start of the welding operation.

Figure 5 is a view similar to figures 3 and. 4;

ill

but illustrating the completion of the welsh operation.

Figure 6 is a vertical cross-sectional view taken through the laminated sheets produced by the welding operation illustrated in Figures 3 to 5.

Figure l is an isometric View of a piston ring prepared from a strip oi the Welded sheet shown,

Figure 8 is an electrical diagram illustrating sheet composed of steel. and a non-ferrous alloy bonded thereon.

Figure ii is a side elevational view oi a strip cut from the laminated sheet shown in Fl 10 and illustrating the manner in which the strip is bent into piston ring shape.

Figure 12 is a diagram tic view of a com= pressing operation on a wide strip cut from the laminated sheet illustrated in Figure 10.

Figure if is a vertical cross-sectional view taken along the line XXII-X10131 of Figure 312.

Fe M is a vertical cross-sectional view taken along the line nib-XIV oi Figure '7.

As shown on the drawings:

In Figure l the reference numeral l0 designates generally a sheet oi steel suitable for forming the body portion of a piston ring.

In Figure 2 the reference numeral fli designates a sheet of oil-absorbent bearing material such as @ilite. Qilite hasthe following formula:

Percent Copper 00.5 Tin 10 .0 Graphite 1.5

This alloy will absorb appreciable amounts of oil therein and isself=lubricating due to its graphite content. The sheet if! can obviously be composed of other oil-absorbent alloys that are used for bearing purposes, such as various bronzes.

In Figure 3 the reference numeral 62 designates one electrode of a flash-percussion welding apparatus. The reference numeral i0 designates the other electrode of the apparatus.

The electrode 82 carries a support it for the steel sheet 00. This support it has downturned flanges No for receiving the sheet i0 thereagainst. The sheet i0 is longer than the interior dimensions of the support 60 so that it is bowed as shown in Figure 3 when inserted in the support.

The electrode it carries a flat plate 65 on which is mounted the Oillte" sheet it.

In the flash-percussion welding process, the facing surfaces of the sheets i0 and i i are melted in the almost instantaneous period of time during which these faces are brought together. The speed with which the surfaces are brought into complete area contact is so great that any considerable arcing between the sheets is prevented, thereby avoiding oxidation of the surfaces.

The bowing of the sheet 60 in the support M makes possible a contacting oi the end of the sheet H v with the sheet id as shown at i0l6 in Figure 4 as the electrodes 02 and i3 are brought together. This efiects a good initial contact between the sheets, the area of which is almost instantly increased to the whole area of the sheet ii during the percussion stroke. The sheet 40 is flattened intermediate its ends, as shown in Figure 5, as the electrodes are brought closer together. Since good contact is provided during the flattening out oi the bowed sheet 80, arcing between the sheets is largely prevented.

The end portions i'llll oi the sheet 80 are trimmed flush with the ends oi the Oilite sheet H to form a laminated sheet it such as illusw. ted I aaoaeoo I trated in Figure 6. The sheet I8 is composed of the sheets 60 and ii integrally welded together at it.

'In Figure 7 there is illustrated a piston ring '20 formed from a strip cut from the laminated sheet to. The piston ring 20 has the interior body portion ltd formed of steel from the sheet "I while the cylinder-engaging face [lid of the piston ring is formed from the alloy of the sheet H. The thickness of the face layer tic is satisfactorily of the order of magnitude of inch.

The electrical diagram shown in Figure 8 illustrates the wiring of an apparatus for the ilashpercussion welding together of the sheets l0 and i i. This apparatus includes the electrodes l2 and it described in Figures 3 to 5.

In Figure 0 the reference numeral 25 designates power lines supplying alternating current to a transformer 20. A half-wave rectifier 20 is provided in the circuit md includes a plate '28 therein receiving current from the transformer 26. The filament 20 of the rectifier is heated by a battery or other source of current 00 in accordance with usual rectifier installation practice. A variable resistor 30 is mounted in the circuit from the rectifier 271 and a variable condenser 32 receives the charge from the rectifier. The other side of the condenser 32 is connected directly with the transformer (26.

The condenser 32? is connected on one side to a variable inductance element 33 and this element, in turn, is connected to the electrode it. The other side of the condenser 32 is directly connected to the electrode The flash-percussion weld is accomplished instantaneously by the use of condensers and by discharging a high-frequency current into each of the two piecesto be welded. This frequency is varied for the type of metal to be welded and'for the size of the welding area. For example, in welding an area of about two square inches the current used would be approximately 8,000 microfarads, at 4,000 volts and 150,000 amperes. The weld is completed in less than 3 of a second.

The great speed oi the welding operation prevents oxidatlon. The surfaces of the metal sheets to be welded are melted to almost a monomolecular depth. The weld is probably not over 0.0005" in depth.

In the operation of the circuit illustrated in Figure 8, the condenser 32 is charged for one or two seconds and then discharges its load to the electrodes l2 and it. The sheets to and H on these electrodes are charged with the high-frequency current and are brought into contact as shown in Figure 4 with great speed so that the condition illustrated in Figure 5 is reached within ,4 of a second. The sheets are brought together with a percussive force of the order of magnitude of 30,000 lbs. per square inch which causes the molten surfaces of the sheets to form an integral bond therebetween.

In Figure 9 there is illustrated another method of forming a laminated sheet composed of a layer of an oil-absorbent non-ferrous alloy integrally joined with a sheet of steel. As shown in Figure 9 a steel sheet 30 is coated with molten bronze, such as Oilite orother suitable bearing metal 35, as by pouring from a spout 36. The molten metal 35 is poured on the steel sheet 34 in a non-oxidizing atmosphere so as to become integrally brazed or welded to the sheet 34, as

nates generally a laminated sheet formed either by the process illustrated in Figure 9 or by the process illustrated in Figures 3 to 5. This laminated sheet is out along the dotted lines ll into a plurality of strips such as 42 shown in Figure 11. The strip 42 is bent, as by a coining operation, into a piston ring l3, as shown in dotted lines in Figure 11.

If desired a strip 2 can be prepared of greater width than is desired for a piston ring but of less thickness than the piston ring thickness. Such strips can then be upset edgewise for decreasing the width and increasing the thickness of the strips. The operation is illustrated in Figure 12, wherein a wide strip "a composedof a steel layer 44 and an, Oilite layer 45 is passed between hammers or die heads 48 and 41 to form the strip 48.

As best shown in Figure 13, this strip 48 is composed of the Oilite layer l5 and a steel layer 44 with the "Oilite layer forced into the steel layer in the central portion of the strip. Thus the line or area of weld I! is curved .or bowed in section. The steel layer 44 has a concave face while the Oilite layer 45 has a convex face welded to the concave face of the steel layer. This is in contrast with the flat 'area of weld I9 between the Oilite layer II and the steel layer it of the piston ring 20 shown in Figure 14.

The upsetting operation besides working the metals somewhat to impart desired metallurgical properties thereto, thus increases the extent of the area of weld in the finished piston ring.

It has been found that thin steel sheets are easier to. handle in the flash-percussion welding operation and also in the brazing operation illustrated in Figure 9.

If desired the upsetting operation may be effected by the use of pressure rolls' instead of by the dies or hammers shown in Figure 12.

It should be understood also that the process steps illustrated in Figures 3 to'5 may be reversed with the Oilite sheet seated in the support It and the steel sheet seated on the support ll. Likewise the support l5 can be magnetized to attract and hold the sheets I0 and II after lamination to insure the removal of the laminated sheet from the support H.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and L therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

1. A piston ring comprising a resilient split steel ring having a non-ferrous oil-absorbent alloy strip welded thereto to form a self-lubrialloy and steel than cating bearing face thereon, said ring and strip being thickened by an upsetting operation transverse to the weld linetherebetween that effects an increase in the area of weld between the strip and ring.

2. The process of making piston rings which comprises bowing a sheet of metal in a support shorter than the sheet, bringing a shorter flat sheet of metal into initial contact with said bowed sheet, effecting an electrostatic discharge through said'sheets while said sheets are brought together under a percussion impact to melt the facing surfaces of said sheets'and weld said surfaces together, trimming the ends of the initially bowed sheet flush with the ends of said shorter sheet, cutting the laminated sheet 'into strips' and forming said strips into piston rings.

3. A piston ring comprising an inner steel ring member having a concave outer periphery and an outer relatively thick alloy ring composed of copper, tin and graphite having a convex inner periphery welded to the concave outer periphery of the steel ring to form a cylinder-engaging bearing face for the ring, said concave and convex" peripheries formed by compressing the metal in a plane transverse to the line of weld.

4. The process of making piston rings which comprises welding a surface layer of metal alloy bearing material onto a broad face of a steel sheet, cutting the resulting laminated sheet into strips of greater width than required for piston rings, upsetting the strips in a plane transverse to the line of weld to flow the steel and alloy into a concavo-convex curve along the weld line thereby simultaneously reducing the strips to the approximate desired width and producing in the upset strips a greater weld area between the that obtainable in non-upset strips of like width and bending the upset strips into piston ring form.

5. The process of making piston rings which comprises bowing a sheet of metal, bringing a fiat sheet of metal into initial contact with said bowed sheet, effecting an electrostatic discharge through said sheets while said sheets are brought together under a percussive impact to melt the facing surfaces of said sheets and weld said surfaces together, cutting the resulting laminated sheet into strips, and forming said strips into piston rings.

6. A piston ring comprising an inner steel band, and an outer metal alloy band welded along its inner face to the outer face of the inner band to form a cylinder-engaging bearing surface, said welded together bands being thickened by an upsetting operation transverse to the weld line therebetween that effects a flowing of the steel and alloy into a concave-convex curve along the weld line.

ARCHIE T. COLWELL. 

